Today commemorates the 20th anniversary of the deadly terrorist attacks against the United States. Also, it marks the appearance of a true hero, Betty Ann Ong, a flight attendant who alerted the country of the attacks on Sept. 11, 2001.

During her last 25 minutes of life, Betty used the emergency line on American Airlines Flight 11 to call the ground crews, calmly providing information about her plane’ hijackers.

At 8:20 a.m. that day, Betty spoke in a low voice on an Airfone from the rear of Flight 11: “The cockpit’s not answering. Somebody’s stabbed in business class—and I think there’s Mace … I think we’re getting hijacked.”

Thanks to her furtive phone call, U.S. authorities were able to identify five hijackers taking control of American Airlines Flight 11, one of four hijacked planes that day. The plane was bound for Los Angeles out of Boston’s Logan Airport, but 14 minutes after takeoff, it made a U-turn and headed toward New York City.

When the plane crashed into the World Trade Center’s North Tower at 8:46 a.m.–the first of two planes to fly into the towers, Betty along with the other 10 crew members and 81 passengers, died.

Her last words were heard: “Pray for us. Pray for us.”

Betty, a 45-year-old Chinese-American, would have had a different destiny if she had not asked to work an extra shift on Flight 11 on that day so she could join her sister Cathie for a vacation in Hawaii, according to New York Post.

Her early and detailed account of what was occurring helped the U.S. government realize the extent of the day’s attacks by al-Qaeda and the Federal Aviation Administration could take the unprecedented step of grounding flights nationwide.

Betty was declared “a true American hero” in 2004 by the 9/11 Commission for her courage and contribution.